NEC Commercial Electrical Practice Test

When using aluminum or copper-clad aluminum grounding conductors outside, how far must they be terminated from the earth?

1. 6 inches

2. 12 inches

3. 18 inches

4. 24 inches

The correct answer is: 18 inches

The requirement to terminate aluminum or copper-clad aluminum grounding conductors at least 18 inches from the earth is rooted in both safety and material integrity. This distance ensures that the conductors are protected from potential damage due to moisture or soil conditions, which may lead to corrosion over time. Terminating at this specified height helps maintain the integrity and performance of the grounding system, ensuring that it functions effectively even in adverse outdoor environments. The 18-inch requirement provides a balance between accessibility for maintenance and minimizing exposure to elements that could degrade the conductor. While other termination distances might seem reasonable in specific contexts, they do not align with the established standards for grounding conductors and fail to address the potential risks associated with grounding systems exposed to environmental factors.